X-ray tube comprising a liquid cooled anode



Aug. 9, 1955 B. COMBEE ET AL 2,715,194

X-RAY TUBE COMPRISING A LIQUID COOLED ANODE Filed Nov. 19, 1952 IN VEN TORS BART coMBE JACOBUS MARINUS HOUTMAN BY %M/%7% AGENT Uniteo X-RAY T UBE COMPRISING A LIQUID COOLED AN ODE Bart Combee and Jacobus Marinus Houtman, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application November 19, 1952, Serial No. 321,420 Claims priority, application Netherlands December 3, 1951 4 Claims. (Cl. 313-32) In X-ray tubes, liquid-cooling is employed in order that the heat produced in the anode shall be carried off rapidly. An improvement of the use of a continuous stream of liquid along the surface to be cooled consists in providing a spraying device having a wall furnished with a large number of holes and spaced closely from said surface. This construction has the advantage of producing a strongly turbulent flow of liquid and of utilising the property that the heat transference to the liquid by turbulence is much higher than in the case of a laminar flow along the surface. The present invention has for its object to improve the results of this cooling method. The larger the number of holes the better the result and this structure is susceptible of simplified and inexpensive manufacture.

According to the invention, which concerns an X-ray tube comprising a liquid-cooled anode, wherein the cooling liquid is supplied through a spraying device to the surface to be cooled, a movable guide for the liquid is provided between the hot surface and the wall dividing the stream of liquid into thin jets.

It has been found that the use of a spraying device in X- ray tubes comprising an oil-cooled anode, may involve isle formation at the surface to be cooled, which is to be understood to mean that the surface to be cooled is fouled by oil rests baked in places to the surface after the tube has been operated for some time. This is evidently due to laminar currents of low velocity which occur in spite of strong turbulence of the liquid, impurities depositing along the paths followed by said currents. This is probably also due to the temperature at said points becoming so high as to cause decomposition of the cooling liquid when using oil.

A further explanation of isle formation is that when the tube is not in use and placed vertically with the anode up, any solid matter present in the liquid settles down on the surface to be cooled. At points where the stream of liquid is laminar, the layer of sludge is not at all removed or much less rapidly than by the liquid jets. In order for the deposit to be efiectively removed the movable guide may be a brush by which the surface to be cooled is swept.

In order that the invention may be readily carried into effect it will now be described in greater detail with reference to the accompanying drawing which represents one example of an X-ray tube according to the invention and in which:

Fig. l is a longitudinal section of the X-ray tube;

Fig. 2 is a cross-section on the line HII on a slightly larger scale;

Fig. 3 is a modified construction of the invention.

The glass wall 1 of the X-ray tube comprises reentrant end parts 2 and 3 respectively. In the re-entrant part 2, the wall is sealed to a rim 4 of an anode 5. The re-entrant part 3 terminates in a glass stem 6 into which two supply conductor 7 and 8 are sealed.

The anode 5, for example consisting of copper, is provided at its front surface with a disc-shaped plate 9 usually made from tungsten and serving as a target for the electrons from an incandescent cathode 10. Through a stay-wire 11 tates Patent 2,715,194 Patented Aug. 9, 1955 the incandescent cathode is fastened to a metal plate 12 to which a supply conductor 7 is also secured. The supply conductor 8 passes through an aperture 13 in plate 12 and is connected directly to the incandescent cathode. The aperture 13 may be filled up with a plug 14 of vitreous or ceramic insulating material. The cathode structure is fitted in a metal cap 15 which rests on the glass stem 6 and whose front surface is provided with an elongated aperture 16 for the passage of electrons.

The anode 5 exhibits a cavity 17 into which a metal tube 18 extends. This tube opens out into a metal case 19, the diameter of which is a little smaller than that of the anode cavity 17. The flat front surface 20 closing the case 19 is slightly spaced apart from the bottom 21 of the cavity 17 and furnished with a large number of small holes 22 which may be distributed rather arbitrarily over the surface. In view of the liquid, for example water or oil, being supplied under pressure through the tube 18, the wall should not be excessively weakened by said holes and therefore the permissible number of holes is smaller than the quantity desirable for yielding a satisfactory cooling effect. The liquid passes at a considerable rate through the holes in the wall 20 and produces a strongly turbulent circulation in the space between this wall and the bottom 21 of the cavity 17. Even the maximum number of holes which can be provided without substantially weakening the wall yield insufiicient turbulence. After such a tube has been in use for some time, fouling occurs along particular lines of flow at the bottom of the cavity 17. Due to the high temperature of this surface said impurities become baked to it and cause a considerable diminution of the heat transfer capacity of the surface. This disadvantage is avoided by providing a movable liquid guide 23 which, as shown in Fig. 2, is shaped as a vane wheel whose wings 24 are curved in the well known form of blades. The vane wheel is rotatable about a pin 25 fitted to the Wall 20 and is continually operated by the liquid supplied to it. In this manner there are no points in the layer of liquid between the wall 20 and the bottom 21 of the cavity 17 where the stream is so slow as to permit the deposit of impurities.

The cavity 17 is closed by a plate 26 to which is secured a metal exhaust tube 27.

Although still further forms of the movable liquid guide are possible, those are preferred which are so constructed as to be continuously operated by the stream of liquid. One form is shown in Fig. 3 and employs a movable guide 33 having a brush portion 34 which sweeps the surface 21 to be cooled.

What we claim is:

1. An X-ray tube comprising an envelope, a cathode, an anode facing the cathode, said anode having a hollow recessed portion on the side thereof remote from said cathode, means coupled to said hollow recessed portion for introducing a cooling medium therein to cool the anode,

a spraying device positioned in said recessed portion to circulate said cooling medium over a maximum surface area of said recessed portion of said body, said spraying device including a perforated member having a plurality of openings therein and spaced from a wall portion of said recessed portion, and a movable guide member mounted in the space between said wall portion and said perforated member and adapted to be set into motion by said cooling medium whereby the cooling medium will flow with high turbulence over the surface area to be cooled without forming a laminar layer thereon to effect maximum heat transfer from said anode to said cooling medium.

2. An X-ray tube as claimed in claim 1 in which the movable guide is rotatably mounted on the perforated member.

3. An X-ray tube as claimed in claim 2 in which the movable guide comprises at least one blade-shaped vane.

References Cited in the file of this patent UNITED STATES PATENTS Channey Jan. 19, 1932 Warden Sept. 4, 1934 McEuen Mar. 12, 1935 Findlay Mar. 24, 1942 Reiniger Nov. 4, 1952 

